#include <stdio.h>

/*
题目： 一张大饼， 切20刀最多分成多少块
*/

int cutpie(int n) {
    int sum = 0;

    
    if (n == 0) return 1;
    sum = cutpie(n - 1) + n;
    return sum;
}
int main () {
    int n = 0;
    int num = 0;
    printf("please input you want to cut knife_number :");
    scanf("%d \n", &n);


    num = cutpie(n);
    printf(" num = %d \n", num);
    return 0;
}